Thanks for all the input folks.
First of all, the GPS was stolen in the driveway of our home. We had failed to lock the vehicle and activate the alarm, so the thief could work very quietly. Evidently, the motion activated security light didn't deter them. I hadn't filed a police report, but I'll rectify that this morning.
There was NOTHING visible inside the truck. The GPS, mounting bracket and power cable were all located in the center console of the truck. There wasn't even a mark on the windshield from the suction cup.
I didn't think that I'd recorded the serial number of the unit. However, I logged into the Garmin website, and found that I'd recorded the serial number when I registered it for map updates. This gave me the model number, serial number and date of purchase (2007).
Since I'd registered the unit with Garmin, they work with their customers and law enforcement to recover stolen GPS units. Once I provide them with a police report number, they place a flag on the account that the unit has been stolen. If anyone ever tries to update the GPS, and tries to set up an account with this unit, Garmin will flag the police with the information!
I guess if I've learned anything, it's two things. Make certain that the vehicle is locked and alarmed at all times. Also - hurry up and get done with my home remodeling project so I can get the building materials out of my garage and park the truck back inside!